Why do I need to polar align my equatorial mount?

BBC Sky at Night Magazine's Scope Doctor Steve Richards solves your astronomy ailments.

How to set up an equatorial mount

Why do I need to polar align my equatorial mount?

Steve says: “Earth takes 24 hours to complete one revolution on its axis with regard to the Sun. However, because Earth also orbits the Sun, it takes 23 hours 56 minutes and 4.1 seconds to complete one revolution with regard to the stars.

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From an observer’s point of view, the stars appear to move across the sky in an arc from east to west in the northern hemisphere and from west to east in the southern hemisphere.

Therefore, to follow this movement it’s necessary for the mount to rotate in the same plane as Earth by aligning it with the north and south poles.”

Some more guides that may help:

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Email Steve your astronomy queries to contactus@skyatnightmagazine.com and they could be answered in a future issue of BBC Sky at Night Magazine.